How are lots of empty egg trays products that are used for acoustics in a building?

How are they what?

I use empty cardboard egg cartons for plant starters in the spring. Some soil, a little seed, a poke in the bottom for drainage, and there ya go. I plant the seedings right in their little cardboard containers.

If you fix them to the walls they deaden sound… effectively making a soundproof room.

The question is confusing. Are you asking why they are effective? It’s because sound waves get lost in their pores and their rounded shapes, which deadens the sound (as @Cloverfield said). Or are you asking something else?

Empty egg trays are generally not used “professionally” as acoustic dampers.

“egg crate foam” is a style of foam construction used to “cheaply” deaden sound.

The pro ones are generally more pointy: http://www.foambymail.com/soundproofing.html

And actual anechoic chambers look really scary: http://www.ta.chalmers.se/images/CRAG/hemi_anech.jpg

For typical building acoustics, they don’t bother with foam, usually 2” duct liner is just tacked up behind visual screens to absorb extra reflections

The “bumps” of the carton create more surface area per square foot and will thusly have more soft surface to reflect, deaden and absorb the sound waves.

(I think this is a followup to: http://www.fluther.com/disc/75636/what-are-some-products-that-are-used-for-acoustics-in-a/ )

The problem with egg crates is that the paper material is relatively dense (on the order of 43 pounds per cubic foot (pcf)), while something like duct liner is closer to 2pcf

The more dense the material, the more it’s going to reflect sounds, rather than simply absorb them. It’s also going to (similar to a piece of paper) tend to reflect very specific frequencies (higher ones), while letting lower frequencies just pass right through.

@grumpyfish – love that pic. Talk about your surround sound! I’m assuming those are speakers pointed at him.

@stratman37 I believe it’s a chamber designed to electronically model acoustic environments—a lot of acousticians set up chambers similar (of various levels of tech) to explain the difference between e.g., NC20 and NC15 environments (which for something like a concert hall is a couple of million dollars difference), as well as different variable acoustic environments in hypothetical buildings.

sweet!